Abstract
EPR was used to determine the paramagnetic platinum and oxygen species which are present at various stages in the genesis of a supported platinum catalyst and to determine the effect of the support on the formation of such species. Paramagnetic platinum centers, believed to be due to Pt 8+, are formed when Pt(NHa)4+2/A1203 is calcined in 02; for low metal contents a large fraction of the platinum is in the form of these species. Catalysts prepared by the same techniques with SiO2 as a support show no paramagnetie platinum signals. Adsorption of O2 on the Pt/A120a catalysts results in the formation of a 3-g 02- signal and a second 2-g signal due to O- and results in a corresponding reduction in the platinum signal. Again Pt/SiO2 did not show comparable behavior. The results are interpreted in terms of electron transfer to the AlcOa.
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